Which GBS variant involves both motor and sensory axons?

• A. Acute inflammatory demyelinating polyneuropathy (AIDP)
• B. Axonal motor and sensory neuropathy (AMSAN)
• C. Acute motor axonal neuropathy (AMAN)
• D. Chronic inflammatory demyelinating polyneuropathy (CIDP)

Answer: (B)

Guillain-Barré syndrome variants are defined by which nerve components are affected and whether that involvement is demyelinating or axonal, as well as which fiber types (motor or sensory) are involved. The axonal motor and sensory neuropathy stands out because it involves axonal degeneration in both motor and sensory fibers, leading to acute weakness combined with sensory loss. On nerve testing, you'd see reduced amplitudes in both motor and sensory responses, reflecting loss of the axons in those pathways rather than a primary problem with the myelin sheath.

In contrast, demyelinating types primarily disrupt the myelin around nerves, which slows conduction velocity and can affect both motor and sensory fibers but with a demyelinating pattern rather than pure axonal loss. A form that affects motor axons only would spare sensory fibers, and a chronic demyelinating form would have a longer course rather than an acute axonal pattern.